<!doctype html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>栅格系统</title>
    <link rel="stylesheet" href="css/bootstrap.css">
    <style>
        .container .row div:nth-child(n+1){
            background-color: skyblue;
            margin-top: 10px;
            border: 1px dashed red;
        }


    </style>
</head>
<body>
<div class="container">
    <div class="row">
        <div class="col col-sm-3 col-md-1">第1列</div>
        <div class="col col-sm-4 col-md-2">第2列</div>
        <div class="col col-sm-5 col-md-9">第3列</div>
    </div>
</div>



<script src="node_modules/jquery/dist/jquery.slim.js"></script>
<script src="js/bootstrap.bundle.js"></script>
</body>
</html>